There is a rich literature documenting racial and ethnic disparities in the trajectory of cancer care and outcomes. Through analyses of tumor registry and Medicare data, the Principal Investigator and co-investigators have begun to uncover explanatory mechanisms or pathways underlying such disparities. We and others have identified disparities in survival after a diagnosis of cancer, much of which can be explained by delays in diagnosis leading to more advanced stage at diagnosis, and also by less than adequate treatment. There has also been considerable research on patient-level, physician level, and system- level factors that contribute to disparities in the trajectory of care. In this application we will conduct explanatory analyses with Medicare claims data to identify the mechanisms underlying racial disparities in stage of diagnosis of colorectal cancer (CRC), with a focus on the role of CRC screening among older adults. We will also develop methods to measure the performance of individual primary care physicians in providing CRC screening for patients. Of particular interest is how individual physicians' performance contributes to racial disparities in screening use. Aim 1: Determine the rate of screening for colorectal cancer in black and white men and women 65- 75 enrolled in fee for service Medicare in Michigan, New Jersey and Texas from 2001 through 2007. Aim 2: Determine the effect of other subject level (predisposing, enabling, and need) and environment level characteristics of CRC screening and determine the effect of continuity of care with a primary care physician (PCP) on receipt of CRC screening. Aim 3: Describe the variation among PCPs in use of CRC screening and determine how much of the race disparity in CRC screening is explained by PCP as opposed to patient characteristics. Aim 4: Examine the effects of provider characteristics (years in practice, age, volume of cases, primary specialty board certification, affiliation with academic medical centers, etc.) and medical system characteristics (PCPs per capita, gastroenterologists per capita) on the likelihood of CRC screening and also stratified by subjects' race. There are a number of options available to Medicare to promote health and reduce health disparities among its beneficiaries. The results of the mechanistic analyses in this application will allow for the design of interventions targeting the specific points in the trajectory of care that contribute to ethnic disparities in CRC screening. PUBLIC HEALTH RELEVANCE: In the U.S., colorectal cancer (CRC) is the fourth most frequently diagnosed but second leading cause of death among cancers. We will study Medicare data to understand better the reasons for racial disparities in CRC screening rates. With this information, Medicare will be able to design and implement interventions to promote health and reduce health disparities among its beneficiaries.